1. Technical Field
The present invention relates to a method of manufacturing a microlens array substrate, a microlens array substrate, an electro-optic device, and an electronic apparatus.
2. Related Art
An electro-optic device, which includes an electro-optic material (for example, liquid crystal or the like) between an element substrate and a counter substrate, has been known. For example, a liquid crystal device, which is used as a liquid crystal light valve of a projector, can be described as the electro-optic device. In such a liquid crystal device, it is required to realize high light use efficiency. Here, a configuration has been known in which, when the liquid crystal device includes a microlens array substrate, light incident to the liquid crystal device is condensed and light, shielded by a light shielding layer if the light is not condensed, is used, and thus a substantial opening ratio of the liquid crystal device is improved.
The microlens array substrate includes a substrate in which a plurality of recesses are formed on a surface and which is formed of quartz, and a lens layer which is formed to cover the substrate and which has a refractive index different from that of the substrate. In the microlens array substrate, a plurality of microlenses are formed by burying the plurality of recesses in the substrate using a lens layer. The lens layer is formed of a resin material or an inorganic material, and an upper surface of the lens layer is planarized by providing, for example, a cover member, or performing a planarizing process such as a Chemical Mechanical Polishing (CMP) process.
However, with regard to a display area in which the plurality of recesses are formed to be dug down from the surface of the substrate, the upper surface of the lens layer is high in a peripheral area, which is on the outer side of the display area and in which the recesses are not formed, and thus a step is generated on the upper surface of the lens layer. If the step on the upper surface of the lens layer is large, the increase in man hour or the deterioration in evenness of the upper surface of the lens layer is caused when the planarizing process is performed on the upper surface of the lens layer.
In contrast, a method of manufacturing a microlens array substrate (for example, refer to JP-A-2009-294363) is proposed to reduce the difference in thickness of a lens layer (resin layer), that is, to reduce a step on an upper surface of the lens layer by providing a groove part (depressed part) in a peripheral area (lens non-formation area) of a substrate and lowering the height of a non-display area than that of a display area (lens formation area) of the substrate.
According to the manufacturing method disclosed in JP-A-2009-294363, wet etching is performed on the substrate through a mask layer (first hard mask film) which covers only the display area of the substrate, the groove part, which is depressed toward a lower part than the substrate surface of the display area, is formed in the peripheral area, and then the mask layer is removed. Further, the wet etching is performed on the substrate through a mask layer (second hard mask film), which covers the whole surface of the substrate and in which a plurality of openings are provided in the display area, a plurality of recesses are formed in the display area, and then the mask layer is removed.
However, in the manufacturing method disclosed in JP-A-2009-294363, before the mask layer (second hard mask film) is formed to form the plurality of recesses in the display area, a step is formed by the groove part in the boundary of the display area and the peripheral area of the substrate. Therefore, when the mask layer (second hard mask film), which is formed on the whole surface of the substrate, is removed, there is a problem in that a part of the mask layer is not removed and remains at a corner of the step, more specifically, a corner of the bottom surface and the side wall of the groove part. When a part of the mask layer remains, there are cases in which an upper lens layer is peeled together with the remaining mask layer and in which cracks appear in the lens layer because stress is applied to the remaining mask layer. Therefore, a method of manufacturing the microlens array substrate is required which is capable of performing removal such that the mask layer, which is necessary to form the plurality of recesses, does not remain in the display area even when the groove part is provided in the peripheral area of the substrate in order to reduce the step on the upper surface of the lens layer.